It is not which dog looks most like a monk, it is which dog best represents the monks themselves. For the Lhasa is believed to carry the souls of nuns and monks in Tibet. Please read fully what I have posted below.
You truly should only use the Lhasa Apso, as they orignally came from Tibet and are also currently being destroyed by the Tibet invaders (Chinese) who kill them to hurt and insult the monks. I have not read of the Tibetian Spaniel being crucified or slaughtered before the monks as a means to torture the monks, and to try and kill their way of life and their religion.
The Lhasa Apso is suffering, which pains it's Tibetian people. Due to being forced from it's homeland with it's owners and the monks who care for them (for they believe them to hold the souls of nuns and monks) the Lhasa is slowly becoming endangered.
The Chinese take pleasure in making the monks watch them painfully, slowly, and grotesquely slaughter these beautiful, sacred, and highly beloved dogs whom the monks & Dalai Lama believe hold the souls of their brothers and sisters.
The Lhasa Apso has existed in Tibet for thousands of years. A sacred animal, he was kept in temples, monistaries, palaces, and the finest specimens lived with the Dalai Lama himself. Apso means "Tibetan goat". Lhasa's are also known as the 'Lion Dog'.
The Lhasa Apso did not appear in the West (England) until around 1930, (as a gift from the Dalai Lama) because exporting the breed was forbidden. The first official standard was defined in 1934.